Abstract
M.Sc.
This study comprises the preparation and characterisation of new azolinylidene- and
divinylcarbene complexes of chromium, molybdenum and tungsten, from 1-
phenylpyrawle, 1-methylimidazole and 4,4-dimethyl-2,2-thienyloxazoline precursors.
The reaction of 1-phenylpyrazolyllithium with (C0) 6M (M Cr, Mo or W) yields after
alkylation with CH3S03CF3 in THE the two products (C0)5M[C(OCH3X(ONPhNCHC(H)]
and (C0)5M[C(0{CH2}40C113)(aNPhNCH6H)]. A 'H NMR study indicates the
existence of two isomers for each of the two tungsten CO'cli•lexes.
1-Methylimidazolyllithiura reacts with (CO)6M (M = Cr, Mo or W) to give the carbene
complexes (C0)5MK'N(CH3)CHCH14(C I i 3)] after alkylation with CH3S03CF3, and the
imine complexes (C0)5MOCHN(CH3)CH6H] after protonation with SO3CF3. Reaction
of 1-methylimidazolyllithium with the anionic salt (C0)5 Cl = Cr or W), followed by
alkylation with CH3S03CF3 affords both the mono- and bis(carbene) complexes,
(CO)5M[CN(CH3)CHCHN(CH3)] and (C0)41v1[6N(CH3)CHCIRA(CH3)]2.
The complex (C0)5W[C(0 {CH2 } 40C113)(t‘NPhNaldH)] reacts with
phenylethynthiolate to furnish an anionic organometallic synthon that can either be
alkylated or protonated. Protonation leads to two isomeric forms of the metal-coordinated
thioaldehyde, (C0)5W4—SHC(Ph)=C(OCH3)(oNPhNCHell), whilst alkylation with
various electrophilic reagents produces the metal coordinated dithio-esther
(C0)5 W4--S=C [ SCH3] [C(Ph)=C(OCH3)(tNPhNaldH)].
The neutral divinylcarbene complexes (C0)5Cr{cC(a0CH2CMe2N)SC CH} (a) and
(C0)5W{cC(COCH2CMe214)SCH9H} (19) are prepared by reaction of (C0)5MCr with
the 3-lithiated thienyloxazoline, followed by alkylation with CH3S03CF3 . These
complexes are the first examples of coordinated 'divinylcarbenes utilizing the group 6
transition metals, where the carbene carbon shows carbene character. They are also in
another sense unique since the nucleopbutlic heteroatom where alkylation occurs, is situated
outside the coordinated ring-system, and, therefore, more than two bonds removed fro
the carbene carbon atom.